If you're looking for specific repos related to Walrus, like the site-builder or documentation, you can check out walrus-sites, walrus-docs, and awesome-walrus among others, which are also part of MystenLabs' GitHub account.

You can find the main Walrus GitHub repository, which includes all smart contracts in Move, services in Rust, and documentation, at GitHub. It's open-sourced under the Apache 2.0 license and has everything from CLI clients to publisher services that might interest you. The repository is structured with different branches for Mainnet and Testnet, and there's a README to help you get started.